Brewer's yeast (they are called "Zacharomyces Carlsbergensis" are yeasts that form in the production of beer as companion materials. They develop in the pulp of malt (sprouting barley) and hops (a certain herb used in the production of beer) they ferment the beer but not such a strong fermentation and they remain as a sediment at the bottom of the beer , and are also called "bottom beer yeast", because they sink to the bottom of the beer, as mentioned above. There are also other yeasts that rise to the surface of the beer at night in the foam layer. Some of them are used to produce new beer, but most of them are considered waste and are thrown into waste water. Some relieve the bitterness of the beer yeast Because of the hops that give them their bitter taste, by soaking them in a mixed solution of 1%-2% soda or sodium carbonate or ammonium carbonate and washing them in water that neutralizes the alkali with a weak acid solution and drying them. Since beer yeasts are rich in proteins of high nutritional value , they are a source of B vitamins, and some irradiate these yeasts with ultraviolet rays to enrich them with vitamin D.